The present invention relates to security document printing, and, more particularly, to a system in which tamper-resistant, composite electronic form characters are stored in a database and retrieved by a character manager for single-pass printing on print media with a printing system.
There is continuing interest in developing systems to hinder and/or help detect fraudulent alteration or duplication of sensitive documents. Sensitive document types might for example, include negotiable instruments, especially checks and bank drafts, stock or bond certificates, driving licenses, identification cards or papers, passports, betting slips, prize or game awards, tickets, or documents that simply require validating signatures to be affixed thereto, such as contractual agreements.
One common type of attempted fraud simply involves duplication of the sensitive document, for example using a high-quality color xerographic copying process. Another common type of attempted fraud involves selective removal of the ink/toner forming the text on the document and its subsequent replacement by alternative text.
Negotiable instruments and other such security documents are now often over-printed on specially prepared "safety paper" which has a background pattern which is not readily reproducible by a copying process. The information/text specific to the particular document is then printed onto the specially pre-prepared safety paper in a separate printing operation. The background pattern of the safety paper may be visible to the human eye. Such a pattern might comprise a complex, often multicolored, geometrical pattern, or be a watermark which is most visible when the document is held up to the light Alternatively, the background pattern may be a latent mark that becomes visible or legible only upon attempted reproduction on machines such as xerographic photocopiers, or by exposure to certain wavelengths of light (e.g. UV).
A disadvantage associated with the reliance on safety paper lies in the cost of its preparation. To stay one step ahead of potential forgers, it is necessary to constantly introduce new variants of the background pattern which adds still further to cost. Secure storage of the safety paper is also an expensive necessity, since any theft of the paper will give the forger a is platform from which to produce fraudulent documents on the authentic (stolen) safety paper.
A further disadvantage with safety paper is that if local shortages of the necessary safety paper arise at the document printing site this can results in delays to the printing of the desired documents, which can be a serious business or legal problem. For this reason, it would be advantageous if security documents could be generated on demand without necessarily requiring special paper supplies of pre-printed safety background paper.
One known approach to the protection of (document specific) text on security documents involves printing of the text followed by overprinting of this text with security information such as background patterning, or embellishment of some or all of the text. In alternative approaches specially positioned perforations are applied to the document, or the document is coated with chemicals (applied pre or post printing), or holographic transparent tape is fixed over the (document specific) text. A disadvantage with these types of approach is that they involve multiple printing or processing steps which adds to the expense, especially if colored printing techniques are employed. There are therefore advantages in the development of on demand security printing systems in which both the (document specific) text of the document and the security features are applied in a single step (or single pass`).
U.S. Pat. No. 5,291,243 describes such a system for the single-pass printing of an image comprising alphanumerics and a plural color safety background pattern. The image is generated by integrating electronic information from a standard font database with that of an electronically generated safety background pattern, and transmission of this integrated electronic description of the image to a printer. While this system provides the advantages associated with single-pass printing, it has the disadvantage that the image generation system is relatively complex.
It would be desirable to provide an alternative, and less complex, single-pass printing system which employs a database of characters with a (preset) security background. Thus, the need for a separate step of integrating character (font) information with background information is avoided.
It would further be desirable that the single-pass secure printing system could be advantageously employed in combination with other document security features. For example, the combined use of the printing system with safety paper has been found to lead to a particularly secure overall system. It has been found that it can be beneficial, from a security standpoint, if the printing system uses the same toner/ink to print both character and background information. If the same toner/ink is employed, the adhesion characteristics of both the printed characters and background to the substrate will be identical. Selective removal of character(s) or background is thus made more difficult than would be so were different toners/inks of correspondingly different adhesion characteristics to be used for the character and background portions.
Alternatively, different colors of ink can be used for the character and background information respectively, allowing for better visual recognition of any attempted tampering.